On the death of his father, in 246 BCE, Antiochus waged war on his brother Seleucus II Callinicus, in order to seize Anatolia for himself as an independent kingdom. He defeated his brother at the Battle of Ancyra in 235 BC. But Antiochus was at of length entirely defeated, chiefly through the efforts of Attalus, king of Pergamon, who defeated him at the Battle of the Harpasus and drove him out of Anatolia. Antiochus subsequently fled to Egypt where he was killed by robbers in c. 226 BC.